msm: pcie: support controller PHY settings for Gen3 and Gen4

There are PCIe Gen3 and Gen4 PHY related settings which has to be
programmed at the PCIe controller. Add the infrastructure to
support such settings. Settings for Gen3 also needs to be
applied to Gen4 controllers. Move existing settings to the
new infrastructure.

Change-Id: I67c7c3d7c5bfa13ed30c8fca55f941c8cab0a7f0
Signed-off-by: Tony Truong <truong@codeaurora.org>